The majority of the program projects will utilize experimental preparations that require isolation and characterization of adult and neonatal cardiac muscle cells, or cardiocytes. This core will isolate cardiocytes from: 1) the adult cat, 2) the adult mouse, 3) the neonatal rat, and 4) the neonatal mouse. Adult cardiocytes will be isolated from both normal hearts and surgical models of pressure overload hypertrophy. These demands will best be met by a Core Facility where supply purchases, reagent preparation, and routine procedures can be performed with an economy based on scale, with quality control monitored from a centralized, experienced authority, and with time saved by the provision of labor-intensive services in a centralized facility.